Expressions

While USD doesn’t natively support expressions, we’ve introduced this feature to enhance artists’ workflows.

Consider the scenario of managing image sequences where the filepath varies for each frame. USD provides the capability to achieve this using timesamples, but it’s not always the most artist-friendly approach. Expressions, on the other hand, provide an ability to set these values through user interface.

Expressions currently support modifying only string/asset attributes.

The Expression can be set or removed to/from the attribute by right-clicking the attribute name and picking a corresponding item from the Expression menu:

A variable can be set in the input box bellow the below the attribute name. The variables use the following syntax:

${variable}

The variable can be inserted into any place of a string, e.g:

/shots/car${F}.png

Expressions support the following types of a variable:

Variable	Description
F	The number of the current frame as an integer. It uses a four-digits format (e.g. 0001) in order to improve sorting.
FF	The number of the current frame as a float. It uses a four-digits format preceding the decimal point and three digits succeeding it (e.g. 0001.003) in order to improve sorting.

Since the expression was created, the value of an attribute field can be updated by clicking it.